[libvirt] [PATCH v2] qemu: Introduce caching whether /dev/kvm is accessible

[Daniel P. Berrangé]

On Mon, Oct 29, 2018 at 06:34:58PM +0100, Marc Hartmayer wrote:
> Introduce caching whether /dev/kvm is usable as the QEMU user:QEMU
> group. This reduces the overhead of the QEMU capabilities cache
> lookup. Before this patch there were many fork() calls used for
> checking whether /dev/kvm is accessible. Now we store the result
> whether /dev/kvm is accessible or not and we only need to re-run the
> virFileAccessibleAs check if the ctime of /dev/kvm has changed.
> 
> Suggested-by: Daniel P. Berrangé <berrange at redhat.com>
> Signed-off-by: Marc Hartmayer <mhartmay at linux.ibm.com>
> ---
>  src/qemu/qemu_capabilities.c | 54 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 52 insertions(+), 2 deletions(-)

For benefit of those who were not at KVM Forum last week, this patch
is addressing the performance problem described starting here:

   https://youtu.be/H3lw50IKqGo?t=1055


Regards,
Daniel
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